The present invention relates to a light panel, comprising: a light guide having a front surface defining a viewing window, a back surface and sides between the front and back surfaces; and a patterned array of light sources of at least two types, which types are distinguished by the color of light emitted by the light sources of said at least two types, said array being arranged along at least one of the sides, wherein each light source generates in use a divergent light beam of a color into the panel to, in combination, color the panel.
Such a light panel is known, for instance from LCD backlighting.
Light panels having light sources of at least two types, i.e. two colors, have several advantages over light panels with single color light sources, for instance phosphor converted white LED's. The so-called white point is adjustable and not for instance determined by the phosphor mix. The available color spaces which is determined by the combination of the lamp spectrum and the color filter spectra, is increased. Practically any color point can be produced, including white, by controlling and adjusting the light output of the different color LED's and the color space can be increased as a result of the higher degree of color saturation, that can be obtained with light sources of different types/colors.
However, in the light panels with light sources of at least two types/colors, generating divergent light beams into the panel, a considerable length is required for the colors from the distinct types of light sources to mix and provide the desired color, for instance white. This distance is a limitation on the viewing window, because in the known light panels, wherein the light sources are arranged along a single side thereof, the pitch between light sources of the same color is a number of times larger than the light source-to-light source pitch. The light sources in the known array along the single side of the light panel can for instance be provided in a pattern RGB or, when a larger green flux is desirable or when different colors green with respect to wave length or efficacy is/are desirable, RGBG. It will be immediately apparent to one, skilled in the art, that when the light sources are directed into the panel and generate divergent light beams, the length over which the light beams should be enabled to mix, and which therefore can not be used for the viewing window, is considerable.